Recovery of nickel from idle nickel electroplating baths and the production of an iron-nickel master alloy



June 1, 1948.

NICKEL RECOVERY PERCENT A. WESLEY ET AL 2,442,628 RECOVERY OF NICKEL FROM IDLE NICKEL ELECTROPLATING BATHS AND THE PRODUCTION OF AN iRON-NICKEL MASTER ALLOY Filed Oct. 8, 1945 L CONTROL CHART ELECTROLYSIS WITH STEEL ANODES 9O /gii In a 4 /T so A I A V v 70 I 4 ,r J

an l so A 5 J I qa 40 o 20 1o 0 E o 100 00 400 500 600 700 AMPERE HOURS PER GALLON ANDREW WESLEY EDWARD JUDSON HOEHL ra-(a.

INVENTOR.

ATTORNEY.

Patented June 1, 1243 UNITED STAT ES QFF'IEC ET RECOVERY OF NICKEL FROMIDLE NICKEL ELECTROPLATING RATES AND THE PRO DUCTION OF AN IRON-NICKEL MASTER ALLOY Andrew Wesley. Plainfield, and Edward Judson Roehl, Little Silver, N. J assignors to The International Nickel Company, Inc, New York, N. Y., acorporati'o'n of Delaware Application October 8, 1943, Serial No. 505.4461

5 Claims.

The present invention relates to a process for idle. These experts estimated that the idle nickelelectroplating baths contained about 200,000 pounds of nickel which could be employed-advantageously in the furtherance of the war effort- However, none of the experts knew of a satisfactory process which could be fitted .into the .existing equipment of electroplating plants toproduce a salable nickel product economically.

One idea that had been suggested was to evaporate the idle nickel electroplating solution and then roast the impure nickel sulfate to impure nickel oxide. However, some undisclosedusefor the impure nickel oxide would then have to be found and no expert could suggest ause. All.

other suggestion was to precipitate nickel from.

the idle nickel electroplating solution by the addition of sodium carbonate followed. by the conversion of the nickel carbonate so producedto the oxide or some other form. However, all of the experts readily agreed that all the suggested solutions to this problem were not feasible and practical, primarily for economic reasons.

We have found that-nickel can be recoveredeconomically from idle nickel electroplating solutions by electro-deposition as an iron-nickel alloy suitable for use in steel making and similar metallurgical operations. It is Well known that many attempts have been madeto electro-deposit iron-nickel alloys. However, most of the processes suggested for the production of iron-nickel.

alloys involved careful operation of the electrodepositing process with special attention either to the composition of the electrolyte or to the relative areas of the iron and nickel anodes. Thus, for example, Burns and Warner disclosed a process in U. S. Patent 1,837,355 for electro-depositing nickel-iron alloys in which an anode of nickel, a second anode of iron and a cathode are im mersed in an electrolyte composed of nickelous sulfate, ferrous sulfate, nickelous chloride,,fer-

rous chloride, sodium sulfate and boric acid. Thecomposition of the electrolyte or the proportion of the constituents of the Burnsand Warner electrolyte is adjusted so as to make thecathode potentials of r the nickel and iron substantially equal .over the operatingrportion of-the current densityrange, Burnsand Warner prefer to employ a current density of about 4 amperesper square decimeter or about 37 amperes per square foot, employing anodes which provide -a..ratio ofanodic surfaces of aboutv nickel toabout 15% iron.

In U. S.v Patent No. 2,131,427, Crowder discloses a process for producing an iron-.nickel-alloy inwhich thenickel. content does not substantially,

exceed about 5%.. According to Crowders process special electrolyte is employed containing ferrous sulfate, nickel sulfate, hydrofluoric acid and sodium fluoride.

M, P. Thompson reviewed the efiect of iron on'the electro-deposition of nickel 'in an article published in the Transactions of the American Electrochemical .Society, volume XLIV, pages 359-396 (1923). Of course, Thompson was not concerned with the productionof =a nickel-iron alloy but in determining the effect. of small.

amounts of iron of the order of 6=or 7 %,-upon. the

characteristics of the electro-deposited nickel. During ,his .review, Thompson studied. the work done; by Toepfier who found that. in general, a greater proportion of iron' is deposited in the alloy thanuis present in the solution. Glasstone and Symes, in an article published in'the Trans-- actions of the Faraday Society, volume-23,-page 213-226 (1927), found that the-.amount'of iron in .an .electro-deposit increases rapidly with increasing current-density until 'the' maximum is reached, after which'further increase-of the-current causedthe proportion of-iron: in the deposit either .toiremainaconstant or to decrease.

We'have found: that the processes of Burns and Warner and Crowder and thedisclosures and investigationsv of Thompson and Glasstoneand Symes do not provide-the solution to :the

problem of recovering nickel from idlenickel electroplating baths and. producing a master alloy, suitable for use-in steel making and analogous operations'at'an economic cost.- As a matter. of fact, operating accord-ing'to Burns and Warner or= Crowder .would' defeat the" purposeof our'process.

It is an objector the present invention to provide a process for' recovering nickelfrom: idle nickel electroplating. baths. in -aneconomically practical :manner with equipment readily available inthe averagecnickel-electroplatingplant.

It-is anotherobject of the. present invention .to provide a process for producing an iron-nickel process for recovering nickel from idle nickelelectroplating baths employing solely ferrous anodes substantially devoid of nickel or containing less than about nickel.

The present invention also contemplates the provision of a process for recovering nickel from aqueous solutions containing soluble nickel salts and iron salts employing solely as anodes ferrous anodes substantially free from nickel or containing at most about 10% nickel.

Other objects and advantages will become apparent from the following description taken in conjunction with the drawing which is illustrative of the current density control exercised during the electro-deposition of nickel from an aqueous electrolyte employing solely ferrous anodes substantially devoid of nickel or only containing a small amount of nickel, say not more than about 10%.

Broadly stated, the present invention provides for the electro-deposition of an iron-nickel alloy containing more than 5% nickel particularly from idle nickel electroplating baths which may contain, in addition to the usual nickel electroplating salts and the usual buffers, the conventional brightening agents and similar addition agents employed in the art to produce bright nickel electro-deposits and to reduce pitting and the like. In the present process it is not necessary to employ nickel anodes and, as a matter of fact, it is preferred to employ only ferrous anodes such as steel anodes or iron anodes. The steel anodes preferably are of plain carbon steel but may contain small amounts of alloying ingredients. Accordingly, low alloy steels may also be used as anodes.

According to the present invention the electro-deposition of the nickel-iron master alloy is carried out at a pH of about 2.0 to about 5.6 but preferably at a pH of about 4.0 to about 5.0. That is to say, if the solution from which the iron-nickel master alloy is to be electro-deposit-ed has a low pH such as a pH of about 2.0, it is not necessary to adjust the pH before starting the electro-deposition of the nickel-iron alloy. However, as electro-deposition proceeds it is preferred to hold the pH of the solution between a pH of about 4.0 and a pH of about 5.6.

The composition of the electrolyte from which the iron-nickel master alloy is to be electro-deposited is not important provided the nickel is present as a water soluble nickel salt. As those skilled in the art know, conventional nickel electroplating solutions generally contain the nickel in the form of its chloride or sulfate. However, it is not necessary that the nickel be present as the chloride or sulfate. operative even if a portion or all of the nickel is present as salts of nickel other than the chloride or sulfate. Furthermore, it is not necessary that a buffer such as boric acid be present although the presence of a buffer is necessary if a sound, solid alloy deposit is desired.

The potential employed in electro-deposition in the present process is determined by local conditions and the spacing of the anodes and cathodes. That is to say, a potential is employed sufficient to provide the current density within The present process is the limits which have been found satisfactory to produce the iron-nickel master alloy economically. Consequently, the potential will be employed within the limits of the equipment available to produce the current density of about 20 amperes per square foot to about 35 amperes per square foot during the deposition of the major portion of the nickel in the solution and to produce the current density of about 45 amperes per square foot during the remainder of the deposition. As will be made clear hereinafter, the residual nickel can also be removed by operating at current densities of about 5 amperes per square foot. However, the potential employed is only that necessary to produce the current density desired and is not controlled with respect to the composition of the electro-deposit.

The cathode may suitably be a ferrous strip such as plain carbon steel and the like from which, if desirable, the electro-deposited ironnickel alloy may be stripped. On the other hand, if so desired, the electro-deposited iron-nickel alloy need not be stripped from the cathode. In any event, after the electro-deposition has been brought to a conclusion, the deposit is washed, dried and melted or further treated to provide the alloy in a suitable form for use in steel making and analogous metallurgical operations.

In order that those skilled in the art may have a better understanding of the novel process, the following example is illustrative of the recovery of nickel from an idle nickel electroplating solution. The solution contained nickel in the following form and amounts:

Nickel was recovered from a bath having the foregoing composition employing mild steel anodes and a temperature of about 120 F. Two anodes 3 inches by 6 inches by V; inch and a steel cathode having an area of about 0.14 square foot were employed. The anode-cathode spacing was 2.5 inches. The pH of the solution was maintained between 5.0 and 5.6 by the addition of sulfuric acid at suitable intervals. The cathode current density of about 20 amperes per square foot was employed and maintained until 70% of the nickel originally in the bath had been removed as was determined by analysis. During this period a total of about 300 ampere hours per gallon of solution had been passed through the cell. During the next hundred ampere hours little nickel was recovered as is readily recognized by examination of curve I in the drawing. That is to say, curve I is practically parallel to the abscissa for the period during which 300 to 400 ampere hours per gallon were passed through the solution. The current density was then lowered to about 5 amperes per square foot of cathode area and nickel deposition reoccurred. When about of the nickel present in the original solution had been recovered the rate of nickel removal by electro-deposition became too low to be economically practical and electro-deposition was terminated.

The deposit obtained during this electrolysis was a nickel-iron alloy with an average nickel content of about 49%.

In further illustration of the present process an electrolyte similar in composition to that de waite liers nbefo wa irclyz .n ..-ih at er I anodev tocathode spac p pf; about. es. A higher current density, i. e.,,35 amperes aperasquare. foot of cathode-- area, was employed.

Thee lectro-deposition of nickel from the solution under these, conditions became so low after about t 68% hadbeen removedthat the current density lwasincreased to about 45 amperes per square foot.

r;.6. .%1t i.a out;30%;;o ent the electrolyte; .or, during; the passageof ab ntt illfl. ampe e hoursper al on, r u tila ut density was lowered to, about 5 amperes per square re tor cathode; area and the electrolysis continned. Electrolysis at this lowered cathode currentdensitywas equally as satisfactoryas .that

carried out at 45 amperes-per square footof-cathodearea. After the passage of about 7100 ampere hoursper gallon of solution about.88% of the nickelpresent in the original solution had been .rcovered by electro-deposition as an iron-nickel mass having a, nickel content of about 50%. The curve II of the drawing clearly shows that the rate ,of electro-deposition of nickel after the current density hadbeen lowered to about 5 amperesper square foot .ofcathode areawas almost as great .,as .it had been during the original electrolysis period at 35 amperes .per square foot. Curves I and II of thedrawing clearly show that after-the Irate f electro-deposition of nickel at to 35 amperes per square foot drops off, the rate of deposition can be accelerated either-by increasing the current cathode density :to about;45 amperes per square foot or by lowering the current cathode density to about 5amperese per square foot.

In carrying out the foregoing tests, the pH of the solutions, being electrolyzed was maintained;-

between about 5 and about 5.6 (Q); that is to say, the pH of the electrolyte during electrodeposition in the first test was between about 5.0 and 5.6 (Q.) and the pH during the electrodeposition illustrated by the second example was between about 5.3 and about 5.6. I A third-test was carri ed out employing an electrolyte of approxi- ..mately the same composition but having-thepI-I of about 2.0 to about 3.0 (Q). The course of the electro-deposition of the nickel from this electro- .lyte is illustrated by curve III of the drawing. Curve III of the, drawingclearly indicates that nickel recovery is less efficient and more costly at low pH such as pH 2 to 3 (Q), than at high pH such as 4 to.5.6 (Q). However, when recovering nickel from idle nickel electroplating.solutions. it is unnecessary to raise the pH from pH 2 or 3 (Q) by suitable addition of alkaline reagents prior to electrolysis in view of the fact that in a practical period of time the pH of solution rises to within the preferred range. However, when desirable, the pH of the solution from which the nickel is to be recovered may be raised to a pH within the range pH about 4.0 to about 5.6 by the addition of suitable alkaline reagents such as ammonia.

Those skilled in the art will recognize that the novel process described herein involves the use of ferrous anodes at a current density depending upon the amount of nickel remaining in the solution from which the nickel is to be recovered. That is to say, when the solution from which nickel is to be recovered contains about 10 ounces of nickel per gallon, a cathode current density of about 20 to about 35 amperes per square foot is .emp oyed-,during,;=thercmpyal f thezfirstsabolit nickel ;.origina1ly; =pres- 3 ounces of nickel per gallon remain-undeposited. Thereafter, the cathode currentdensity eitheris reduced to about 5 amperes per-square foot of cathpdearea orincreasedto about 45 amperes per square footof cathode area until about '.toabout-90 of the nickel has been recovered by .electro-deposition; as an iron-nickel alloy containing, about 50% nickel. .Furthermore, it is to be. recognized that the, composition of. the electrolyte isnot controlled to provide critical cathode potentials as taught by Burns and Warner,

nor are .nickelanodes as well. as iron anodes -em-.

ployed to obtain. a critical proportion of nickel anode. surfaceto iron. anode. surface. Furthermore, the compositionof the bath is not-controlled within critical ranges to provide a critical nickel toiron composition in the electrolyte.

Although the .present invention has .been describedin conjunction with the recovery of nickel from idle nickel electroplatingbaths.or .solutions, itis to .be recognized thattheprinciples of the .present process can be employed-in the .refining oft nickel to. recovera nickel-iron .prodnot having commercial. value. tThatisto say, refinery liquors containing. nickel and-iron can betreated in accordance with thepresent process to recover the nickel as a nickel-iron alloy suit- ..able for use insteel-making and analogous .metallurgical operations. Furthermore, the present application I has .been .described in conjunction With certain preferred embodiments thereof, .but :those skilled in-the .art.will understand-that variations and modifications thereof may be -made. Such variations and modifications are to beconsidered, within the purview of the present specification .and the .scope-of the appended claims. Thus, for. examplewhile. it is preferred to employferrous, alloys v containing not more than about 10%of. nickel. asanodes in the presentprocess, it is also possible to employ insoluble anodes. However, the use of insoluble anodes increases the potential necessary to-produce the desired current. densityand consequently increases the cost .of operation.

.We-claim:

1. A process for recovering nickelby electrodepositing a mass of iron and nickelfrom electroplating electrolytes without substantially replenishing .the nickel from other sources as nickel is recovered which comprises establishing an aqueous nickel-containing electrolyte having a pI-li between about 4.0 and about 5.6;passing an electric current between a'ferrous anode a nda cathode, maintaining a current density of about 20 amperes per square foot until the nickel content of the electrolyte is reduced to about 3 ounces per gallon without substantially replenishing the nickel from other sources as nickel is plated out of the electrolyte, thereafter employing a different current density of about 5 amperes per square foot without substantially replenishing the nickel of the electrolyte whereby the efiiciency of nickel recovery is markedly increased and continuing the electro-depositlon at said different current density until about of the nickel originally present in said aqueous electrolyte has been electro-deposited at the cathode as a nickel-iron deposit.

2 .A process for recovering nickel by electrodepositlng a mass of iron and nickel from electroplating electrolytes without substantially replenishing the nickel from other sources as nickel ploying a different current density of about amperes per square foot without substantially replenishing the nickel of the electrolyte whereby the efliciency of nickel recovery is markedly increased and continuing the electro-deposition at said different current density until about 85% to about90% of the nickel originally present in said aqueous electrolyte has been electro-deposited at the cathode as a nickel-iron deposit,

3. A process for recovering nickel by electrodepositing a mass of iron and nickel from electro-plating electrolytes without substantially replenishing the nickel from other sources as nickel is recovered which comprises passing an electric current between an anode of ferrous material substantially devoid of nickel and a cathode immersed in a buffered, aqueous nickel-containing electrolyte having a pH between about 4.0 and about 5.6, employing a current density of about 20 to about 35 amperes per square foot until the nickel content of the electrolyte is reduced to about 3 ounces per gallon without substantially replenishing the nickel from other sources as nickel is plated out of the electrolyte, thereafter employing a different current density of about 5 amperes per square foot without substantially replenishing the nickel of the electrolyte'whereby the efiiciency of nickel recovery is markedly increased and continuing the deposition at said different current density until about 85% to about 90% of the nickel originally present in said aqueous electrolyte has been electro-deposited at the cathode as a nickel-iron deposit.

4. A process for recovering nickel by electrodepositing a mass of iron and nickel from electroplating electrolytes without substantially replenishing the nickel from other sources as nickel is recovered which comprises establishing an aqueous nickel-containing electrolyte having a pH between about 4.0 and about 5.6, passing an electric current between an anode of ferrous material having not more than about nickel and a cathode, maintaining a current density of about 20 to about 35 amperes per square foot until the efilciency of deposition of nickel at the cathode beginsvto decrease without substantially replenishing the nickel from other sources as nickel is plated out of the electrolyte, thereafter employing a current density of about 5 amperes per square foot without substantially replenishing the nickel of the electrolyte whereby the efliciency of nickel recovery is markedly increased and continuing the deposition at a current density of about 5 amperes per square foot until about to about of the nickel originally present in said aqueous electrolyte has been electro-deposited with iron at the cathode to provide a nickel-iron mass containing about 50% nickel.

5. A process for recovering nickel by electrodepositing a mass of iron and nickel from electroplating solutions without substantially replenishing the nickel from other sources as nickel is recovered which comprises establishing an aqueous nickel-containing electrolyte having a pH between about 4.0 and about 5.6, passing an electric current between a ferrous anode and a cathode, mainta'ining a current density of aboutv 20 to about 35 amperes per square foot untilthe efficiency of deposition of nickel at the cathode begins to decrease Without substantially replenishin the nickel from other sources as nickel is plated out of the solution, thereafter employing a different current density of about 5 amperes per square foot without substantially replenishing the nickel of the electrolyte whereby the efficiency of nickel recovery is markedly increased and continuing the deposition at said different current density until about 85% to about 90% of the nickel originally present in said aqueous electrolyte has been electro-deposited at the cathode as a nickel-iron deposit.

ANDREW WESLEY. EDWARD JUDSON ROEHL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 788,064 Ramage Apr. 25, 1905 969,773 Cowing Sept. 13, 1910 2,051,433 Bosqui Aug. 18, 1936 OTHER REFERENCES Transactions of the Electrochemical Society, volume 58, pages 357-372 (1930).

Zeitschrift fur Electrochemie, Bd. 40, pages 341-343 (1934).

Zeitschrift fur Electrochemie, Bd. 41, pages 596, 597 (1935). 

